In GERAN (GSM (global system for mobile communications) EDGE (enhanced data rates for GSM evolution) Radio Access Network), a random access channel (RACH) is used by the mobile station (MS) to request a channel from the network, e.g. in order to exchange information, to perform location updating or to start a connection. The RACH, which is a logical channel, is transported over the physical channel via access bursts. Typically, within a GERAN network at least one physical channel (which may be characterized by a time slot number and may be referred to as a timeslot) of a carrier frequency in the uplink direction (i.e. from the MS to the base transceiver station (BTS)) is attributed to the RACH. The corresponding channel on the downlink direction, i.e. from the BTS to the MS may be the Broadcast Control Channel (BCCH) which is used by the BTS to describe the identity, configuration and available features of the BTS to the MSs served by the BTS.
Currently, the output power used for the access burst sent over the RACH is set to the maximum available output power of the MS, in order to maximise the probability that the access burst reaches the appropriate BTS or base station (BS) of the network. The details regarding the implementation of the RACH and the structure of the access burst is provided in the technical specification 3GPP TS 45.008 which is incorporated by reference.
The above mentioned approach for selecting the output power has the effect that the MS uses full power, even when the MS is close to the BTS to which it tries to connect. This may result in unnecessarily high output power when an MS is close to the BS, thus causing additional interference on the radio interface, increasing the power consumption of the MS, and causing potential receiver issues in the base station (due to the very high received power level).
Machine type communication (MTC) devices, e.g. stationary devices such as smart meters, may be located relatively far from their serving base station (which may be the nearest base station of the telecommunications network, but which is not always the case). In addition to the geographic distance, the MTC devices may be placed at locations which are shielded from the radio network, e.g. in the basement of a building. As such, the “distance” of a device to the BS (from a radio link point of view) may be due to the geographical distance, as well as due to obstacles on the radio path between the device (MS) and the BS. As a result of such greater “distances”, MTC devices may have the disadvantage of a lower received signal level for the RACH at the receiving base station compared to devices located relatively near to the same base station. This imbalance typically results in a lower probability for a successful channel access for stationary MTC devices.
The present document addresses these issues. In particular, the present document addresses the issue of balancing the probability of a successful channel access for different mobile stations which are served by a particular base station within a wireless telecommunications network such as GERAN.